Make use of call on Function exempt from warnings,

docs/language/dartLangSpec.tex

 \documentclass{article}
 \usepackage{epsfig}
 \usepackage{color}
 \usepackage{dart}
 \usepackage{bnf}
 \usepackage{hyperref}
 \usepackage{lmodern}
 \newcommand{\code}[1]{{\sf #1}}
 \title{Dart Programming Language  Specification \\
 {\large Version 1.10}}
@@ skipping 3855 matching lines @@
 \end{code}
 
 \commentary{Notice that the wording carefully avoids re-evaluating the receiver $o$ and the arguments $a_i$. }
 
 \LMHash{}
 Let $T$ be the  static type of $o$. It is a static type warning if $T$ does not have an accessible  (\ref{privacy}) instance member named $m$ unless  either:
 \begin{itemize}
 \item
 $T$ or a superinterface of $T$ is annotated with an annotation denoting a constant identical to the constant \code{@proxy} defined in \code{dart:core}.  Or
 \item  $T$ is \code{Type}, $e$ is a constant type literal and the class corresponding to $e$ has a static getter named $m$.
+\item $T$ is \code{Function} and $m$ is \CALL. \rationale {The type \code{Function} is treated as if it has a \code{call} method for any possible signature of \CALL. The expectation is that any concrete subclass of \code{Function} will implement \CALL. Note that a warning will be issue if this is not the case. Furthermore, any use of \CALL on a subclass of \code{Function} that fails to implement \CALL{} will also provoke a a warning, as this exemption is limited to type \code{Function}, and does not apply to its subtypes. 
+}
 \end{itemize}
 
 \LMHash{}
 If $T.m$ exists, it  is a static type warning if the type $F$ of $T.m$ may not be assigned to a function type. If $T.m$ does not exist, or if $F$ is not a function type, the static type of $i$ is \DYNAMIC{}; otherwise the static type of $i$ is the declared return type of  $F$.  
 
 \LMHash{}
 It is a compile-time error to invoke any of the methods of class \cd{Object} on a prefix object (\ref{imports}) or on a constant type literal that is  immediately followed by the token `.'.
 
 
 \subsubsection{Cascaded Invocations}
@@ skipping 268 matching lines @@
 
 \commentary{
 This restriction is in line with other limitations on the use of prefixes as objects. The only permitted uses of $p\#m$ are closurizing top level methods and getters imported via the prefix $p$. Top level methods are directly available by their qualified names: $p.m$. However, getters and setters are not, and allowing their closurization is the whole point of the $e\#m$ syntax.
 }
 
 \LMHash{}
 Let $T$ be the static type of $e$. It is a static type warning if $T$ does not have an accessible instance method or getter named $m$ unless either:
 \begin{itemize}
 \item $T$ or a superinterface of $T$ is annotated with an annotation denoting a constant identical to the constant \code{@proxy} defined in \cd{dart:core}. Or
 \item $T$ is \cd{Type}, $e$ is a constant type literal and the class corresponding to $e$ declares an accessible static method or getter named $m$.
+\item $T$ is \code{Function} and $m$ is \CALL.
 \end{itemize}
 
 The static type of $i$ is:
 \begin{itemize}
 \item The static type of function $T.m$, if $T$ has an accessible instance member named $m$.
 \item The static type of function $T.m$, if $T$ is \cd{Type}, $e$ is a constant type literal and the class corresponding to $e$ declares an accessible static member or constructor named $m$.
+\item \code{Function} if $T$ is \code{Function} and $m$ is \CALL.
 \item The type  \DYNAMIC{} otherwise. 
 \end{itemize}
 
 \subsubsection{Named Constructor Extraction}
 \LMLabel{namedConstructorExtraction}
 
 \LMHash{}
 Evaluation of a property extraction $i$ of the form \NEW{} $T\#m$ proceeds as follows:
 
 \LMHash{}
@@ skipping 3617 matching lines @@
 
 The invariant that each normative paragraph is associated with a line
 containing the text \LMHash{} should be maintained.  Extra occurrences
 of \LMHash{} can be added if needed, e.g., in order to make
 individual \item{}s in itemized lists addressable.  Each \LM.. command
 must occur on a separate line.  \LMHash{} must occur immediately
 before the associated paragraph, and \LMLabel must occur immediately
 after the associated \section{}, \subsection{} etc.
 
 ----------------------------------------------------------------------